Flowers are losing their scent

Flowers lose fragrance as global temperatures rise

Israeli student scientist wins award for groundbreaking research on the effect of climate change on plants’ production of pleasing perfume.

June 16, 2016

Photo by Evgeny Bakharev/

Photo by Evgeny Bakharev/

The diverse and delicious fragrances of flowers are among life’s simple pleasures.

However, the biochemical mechanism that causes flowers to emit a perfumed smell is complex. Dozens, and sometimes hundreds, of volatile substances are mixed and released as a way of attracting pollinating insects to the flowers’ reproductive organs.

Scientists have known for some time that increasing temperatures associated with global climate change have a negative effect on plant growth. A Hebrew University of Jerusalem PhD student recently won a prize for his unique research showing that higher air temperature also leads to a decrease in the production of floral scents.

“Increases in temperature associated with the changing global climate are interfering with plant-pollinator mutualism, an interaction facilitated mainly by floral color and scent,” Alon Cna’ani explained in his research.

During his work in the laboratory of Prof. Alexander Vainstein in the Robert H. Smith Institute of Plant Sciences and Genetics on the Rehovot campus, Cna’ani discovered that two types of petunias grown in elevated temperature conditions are significantly defected in production and emission of scent compounds.

The problem is linked to arrested expression and activity of proteins that facilitate biosynthesis of the compounds. Cna’ani demonstrated an approach to bypass this adverse effect by stimulating the expression of a certain gene that boosts the production of scent regardless of the ambient temperature. His research was published last summer in Plant, Cell & Environment.

In June, Cna’ani received the Smith Vision Prize in Agriculture for his body of research, which has included projects aimed at finding novel strategies used by plants to regulate, or fine-tune, the process of scent emission.

PhD student Alon Cna'ani shaking hands with David Bruce Smith at the award ceremony on June 1, 2016, at the Hebrew University of Jerusalem. Photo by Douglas Guthrie

PhD student Alon Cna’ani shaking hands with David Bruce Smith at the award ceremony on June 1, 2016, at the Hebrew University of Jerusalem. Photo by Douglas Guthrie

The Smith Vision Prize was established by David Bruce Smith in memory of his father Robert H. Smith, benefactor of the Faculty of Agriculture, Food and Environment.

According to the university, the prize “is awarded annually to a PhD student whose research best reflects the vision of Smith in feeding the world through sustainable agriculture and whose research shows potential for applicability in fields relevant to agriculture, food and environment.”

Gene of scents

Cna’ani also characterized the first gene (PH4) that functions as a direct regulator of scent emission.

When he manipulated the expression of this gene to a halt, the petunias ceased to emit scent, but continued to produce it. He theorizes that PH4 serves as a switch between two crucial floral traits — color and scent. This research was published in New Phytologist in November 2015.

Now Cna’ani is researching strategies to overcome the decrease in production of beneficial volatile substances, a process that requires a huge energy investment from plants. He’s also investigating a process called glycosylation, in which flowers use a sugar molecule to render scents non-volatile.

His research was funded by grants from the US-Israel Binational Agricultural Research and Development (BIRD), Israel Science Foundation and the Chief Scientist of the Israel Ministry of Agriculture and Rural Development.